add tapering to ft8_downsample.f90

This commit is contained in:
Pavel Demin 2018-10-23 08:44:14 +02:00
parent 87ef78a221
commit df334d9ec7

View File

@ -5,13 +5,22 @@ subroutine ft8_downsample(dd,newdat,f0,c1)
parameter (NMAX=15*4000,NSPS=640)
parameter (NFFT1=64000,NFFT2=3200) !64000/20 = 3200
logical newdat
logical newdat,first
complex c1(0:NFFT2-1)
complex cx(0:NFFT1)
complex dd(NMAX),x(NFFT1)
real taper(0:100)
equivalence (x,cx)
save cx
data first/.true./
save cx,first,taper
if(first) then
pi=4.0*atan(1.0)
do i=0,100
taper(i)=0.5*(1.0+cos(i*pi/100))
enddo
first=.false.
endif
if(newdat) then
! Data in dd have changed, recompute the long FFT
x(1:NMAX)=dd
@ -24,9 +33,9 @@ subroutine ft8_downsample(dd,newdat,f0,c1)
df=4000.0/NFFT1
baud=4000.0/NSPS
i0=nint(f0/df)
ft=f0+8.0*baud
ft=f0+8.5*baud
it=min(nint(ft/df),NFFT1)
fb=f0-1.0*baud
fb=f0-1.5*baud
ib=max(1,nint(fb/df))
k=0
c1=0.
@ -34,6 +43,8 @@ subroutine ft8_downsample(dd,newdat,f0,c1)
c1(k)=cx(i)
k=k+1
enddo
c1(0:100)=c1(0:100)*taper(100:0:-1)
c1(k-1-100:k-1)=c1(k-1-100:k-1)*taper
c1=cshift(c1,i0-ib)
call four2a(c1,NFFT2,1,1,1) !c2c FFT back to time domain
fac=1.0/sqrt(float(NFFT1)*NFFT2)